<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #container {
      position: relative;
      background-color: #000;
    }

    .bubble {
      position: absolute;
    }
  </style>
</head>

<body>
  <canvas id="canvas"></canvas>
  <div id="container"></div>
</body>
<script>
  var canvas = document.getElementById("canvas");
  var ctx = canvas.getContext("2d");

  var image = new Image();
  image.src = "./dragen.jpg";
  image.onload = function () {
    canvas.width = image.width;
    canvas.height = image.height;

    ctx.drawImage(image, 0, 0);

    var imageData = ctx.getImageData(0, 0, image.width, image.height).data;
    ctx.fillStyle = "#ffffff";
    ctx.fillRect(0, 0, image.width, image.height);
    var gap = 6;

    for (var h = 0; h < image.height; h += gap) {
      for (var w = 0; w < image.width; w += gap) {

        var position = (image.width * h + w) * 4;
        var r = imageData[position],
          g = imageData[position + 1],
          b = imageData[position + 2];

        // console.log(`r${r},g${g},b${b}`)

        if (r + g + b < 100) {
          ctx.fillStyle = "#000";
          ctx.fillRect(w, h, 4, 4);
        }
      }
    }

    setTimeout(() => {
      var dragonContainer = document.getElementById("container");
      var dragonScale = 2;

      for (var h = 0; h < image.height; h += gap) {
        for (var w = 0; w < image.width; w += gap) {
          var position = (image.width * h + w) * 4;
          var r = imageData[position],
            g = imageData[position + 1],
            b = imageData[position + 2];

          if (r + g + b < 100) {
            var bubble = document.createElement("img");
            bubble.src = "bubble.png";
            bubble.setAttribute("class", "bubble");

            var bubbleSize = Math.random() * 10 + 20;
            bubble.style.left = (w * dragonScale - bubbleSize / 2) + "px";
            bubble.style.top = (h * dragonScale - bubbleSize / 2) + "px";
            bubble.style.width = bubble.style.height = bubbleSize + "px";
            bubble.style.animationDuration = Math.random() * 6 + 4 + "s";

            dragonContainer.appendChild(bubble);
          }
        }
      }
    }, 1000)
  }
</script>

</html>